I've played it too and man, yeah, that was so short.
But at least the cinematic scenes are really cool, I like them.
Yeah. And as I said, was never fond of the second acts in Shadow Generations. I mean, what's the point in making the side-scrolling when Classic Sonic has nothing to do with them?
So the absence of a second act doesn't bother me.
I think what they could've had been, like with Radical Highway, a boss battle that can be selected. The boss could be either a fight with movie Sonic, Team Sonic or with the G.U.N. helicopter.
(And while the Westopolis remix was awesome, I still wonder if they could've used movie OST... unless the Westopolis mix will be in the movie then
COOL!)